Heating means for billet containers of metal extrusion presses



-May 14. 1957 J. A. LO N ET AL 2,792,482

HEATING MEANS FOR B11. T CONTAINERS oF METAL EXTRU N PRESSES Filed TENgan Haffner -f 5 VENTORS vvvvvvv |N A. Eduard KL.

BY Se e vvvvyvvvvvv v TTORNEYS` HEATING MEANS FR BILLET CONTAINERS OFlMETAL EXTRUSION PRESSES John A. Logan, Youngstown, Ohio, and Eduard K.L. Haffner, Bournemouth, England Application November 30, 1953, SerialNo. 395,228 2 Claims. (Cl.- 219-10.71)

Y Billet` containers of metal extrusion presses are generally equippedwith heating means in order to maintain at the required temperatures thebillets which are extruded from the container. Thesey billets arepreheated before being placed in the container by other heating means,such as those disclosed in United' States Letters Patent, No. 2,676,234dated April 20, 1954.

In the case of some metals, among them light metals and their alloys,the range of temperatures which are most suitable for their extrusion iscomparatively narrow, and close control of the container heating meansis therefore necessary. This requirement is best satisfied by electricheating means. Whilst these were formerly mostly of the resistance type,it has also been proposed to equip the containers of metal extrusionpresses with electric heaters of the induction type. However, none otsuch proposals Ahas so far been satisfactory.

For reasons of economy and eliiciency, it is desirable to produce theheat as closely as possible to the billet chamber of the container.

It is an' object of the invention to provide improved electrical heatingmeans of the induction type for the billet containers of metal extrusionpresses.

The billet containers of metal extrusion presses consist generally ot anumber of parts, substantially in the form of cylindrical shells, whichare arranged one inside the other concentrically to the axis of thecontainer; they are rmly secured to each other by shrinking orotherwise, in order to withstand the high mechanical pressures toWhichth'ey are subjected during the extrusion of thev billets. In someinstances, a container comprises only two such parts, a mantle orcasing,v and a liner which forms the Wall of the billet chamber. As theliner is exposed to continuous wear and has, therefore, to be replacedfrom time to time,y it is generally' made Vas thin' aspossible andcompatible with the, requirements of mechanical strength, and itsthickness is therefore small compared with that of the mantle or casing.In some instances, the container consists of three parts, a liner holderbeing interposed between the mantle or casing and the liner, thethickness of the liner holder being substantially the same as that ofthe liner.

The invention is particularly applicable, although;l not restricted, tocontainers which consist of a mantle or casing and a liner only. Y

According tothe invent-ion, the electric heating means for a billetcontainer of a metal extrusion press comprise one or more inductioncoils accommodated in a recess or recesses provided in a wall of one ofthe aforementioned container parts, the wall being co-axial with thebillet chamber or" the container. The heating means according to theinvention are thus located between casing and liner, or casing and linerholder, and in either case in close proximity to the billet chamber.

This arrangement results in concentrating the magnetic ilux inside theliner and also partly inside the billet chamber and in reducingappreciably the magnetic flux through the outer parts of the container,in particular the mantle sol or casing, whereby the efficiency of theheating means is greatly improved, with a consequent reduction of theelectric energy required.

The coils or coils forming the electric inductor have preferably spiralturns co-axial to the billet chamber. Accordingly, the recesses orgrooves accommodating the turns are of spiral or helical shape. Themachining of these recesses or grooves can be easily carried out.

According to the invention, the recess or recesses provided for theaccommodation of the heating coil or coils are preferably located, inthe case of two-part containers in the casing, and in the case ofthree-part containers in the liner holder, without, however, beinglimited thereto.

The concentration of the heating eiect on the internal parts of thecontainers with the external parts remaining practically cold, has theresult that the internal parts alone will undergo a thermal expansionwhen the heating coils are energized. Thus, in normal operation of theheating means, a shrinking of the internal parts into the external partswill take place to the same degree as that so far achieved during theassembly of the container. ri`his makes it possible to dipense to alarge extent, if not entirely, with the special shrinking operation towhich the container parts had formerly to be subjected at the time oftheir assembly. This is an important additional advantage of theinvention.

Several embodiments of the invention are shown by way of example in theaccompanying drawings, in which:

Fig. l is a section through a two-part container provided with heatingmeans according to the invention.

Fig. 2 is a section taken along line II-Il of Fig. l.

Fig. 3 is a transverse section of an insulated electrical conductor fromwhich the heating coils may be formed.

Fig. 4 is a diagram of electric circuits employed for energizing anelectric inductor built into a container.

Fig. 5 shows on an enlarged scale a portion of a container part withrecesses formed therein.

The billet container shown in Fig. l comprises an external part in theform of a mantle or casing 30, and an internal part in the form of aliner 5, the liner having a straight-through bore of uniform diameter,dening the billet chamber 5a. The billet chamber is, at both its ends,slightly flared, to provide a seat for the conventional extrusion die,not shown here. In the embodiment shown, the liner 5 has a tapered t inthe mantle or casing 30, but this is not essential as the invention canalso be applied to liners having a cylindrical t in the mantle.

The liner 5 is usually made of high-grade alloy steel which must be ofvery high tensile strength, even when heated up to elevatedtemperatures, whilst the requirements for the mantle or casing aresomewhat less exact.- ing. For this reason, and also because it has tobe renewed from time totime, the wall thickness of the liner 5 is smallcompared with that of the mantle or casing 30.

According to the invention, the interior wall of the bore of the mantleor casing is provided with recesses having in the `embodiment shown theform of a helical or spiral groove 3% which is adapted to accommodatethe convolutions or turns of one orrnore coils forming' an electricinductor.

vPlconfciuctor'li ior'suc-h a' coil'is `shown inY detail in Fig. 3, andcomprises a base portion 15 which may be formed of a copper bar. Weldedto the base portion at l2 is a tubular portion 14 forming a conduit Ofor a coolant. The conducto-r has an outer insulating wrapping 13.

The depth and cross-section of the spiral groove 301; is such that theconductor 11 can be tightly forced within, the conductor beingperferably cemented in the groove by temperature-resistant material orotherwise.

The coil or coils are preferably embedded in the recessor recesses ofthe container parts in such a manner that they do not protrude radiallyover the surface of that part so as to permit its unobstructed axialmovement relative to the adjacent part of the container.

The inductor may comprise a single coil winding which may be energizedfrom one phase of a three-phase source. The preferred arrangement is,however, one shown in Fig. 4 and in which three separate coils 1, 2 and3 are used which are fed through transformers 23, 22 and 21 from themains 51, 52 and 53 of a three-phase source, through a set of switches61, 62 and 63, operated by a solenoid 10 and through conductors 71, 72and 73. Connected to the primary windings 93, 92 and 91 of eachtransformer are tap switches 43, 42 and 41 which enable the voltage ofeach of the transformers to be independently regulated. For a completedisclosure of the electrical circuits shown i-n Fig. 4, reference may bemade to the copending application of Bruce E. McArthur for LettersPatent, identitied as Serial No. 303,342, tiled in the United StatesPatent Ofiice on July 29, 1952, now Patent No. 2,748,240.

The coils 1, 2 and 3 are connected to their respective transformers 23,22 and 21 through conductors 31, 32 and 33 respectively attached tothe'ends of the coils and accommodated in axially spaced-apartpassageways 25 of the container mantle 36. As shown in Fig. 2, thepassageways 37 in the middle of the mantle each accommcdate a pair ofconductors, one for each of a pair of adjacent coils. The conductors arecovered with insulating material which may be of the same `nature as thewrapping 13.

Each of the coils 1, 2 and 3 is fed by one of the phases from thethree-phase source indicated by the mainsI 51, 52 and 53. As shown inFig. 4, the conductors 32 of the centre coil 2 are transposed, wherebythe phase .diiierence between the magnetic elds of two adjacent coils isonly 60 instead of 120, thus minimizing the dispersal of magnetic linesof force in those regions where two adjacent coils face each other. Inother words, the phase relationship between the three coils 1, 2, and 3with the terminals 32 of the centre coil 2 transposed is similar to onebetween three successive phases of a. siX- phase system.

Whilst Fig. 4 shows three axially-aligned coils, it will be understoodthat the inductor may comprise any desired number of coils, and thesemay be energized in other ways than those shown in Fig. 4.

It is frequently desired to concentrate the heating effect at one orboth ends of the billet chamber 5a, as more heat is lost at the ends ofthe container and the billet chamber than at the centres for obviousreasons; one way of achieving this result is to feed the outer coilswith a stronger electric current than the centre coil, which may beattained by suitable regulation of the transformers 23, 22 and 21 bymeans of the tap switches 43, 42 and 41. A similar result can beachieved by giving the two outer coils a smaller number of turns thanthe centre coil, or by placing the turns of the two outer coils moreclosely together than those of the centre coil.

Similar results can also be obtained by providing coils at the two endsof the billet container only, leaving the middle part without anyheating means. This arrangement is particularly suitable where theheating means comprise only two coils.

A thermo-couple element or any other thermo-responsive device may beapplied to the parts of the container in which the heating meansaccording to the invention are arranged.

The invention is not limited to the embodiments shown and describedhere, and a variety of other arrangements of the electric inductorwithin the container can be evolved within the scope of the invention,the main object remaining always the provision of an electric inductorin the proximity of the billet chamber of the container of a metalextrusion press.

What is claimed is:

1. The combination with a metal extrusion press, a billet container formaintaining a contained metal at a desired extrusion temperature, saidcontainer comprising a pair of stationary relatively telescoped tubularouter mantle and inner liner elements of which the liner element has anaxial cylindrical bore affording a pair of opposite end openings, and anouter wall surface which is of frusto-conical form to cause the wallthickness of said liner to be progressively decreased to a substantialdegree, proceeding from a first end of the liner to its longitudinallyopposite end thereof, said mantle having an inner wall surface which islongitudinally tapered complementary to the tapered of the outer wall ofsaid liner, and said interior mantle wall being provided with a spirallyrecess, spirally formed induction coil conductor means embedded in saidmantle recess, the inner Wall surfaces of said mantle beingcompressively tightly inteitted with the outer wall surfaces of saidliner, and electrical means for communicating alternating current tosaid conductor means to energize the same, said container being securedby that one of its longitudinal ends, whereat said liner walls are ofleast thickness, and where said mantle walls are of greatest thickness,to the extrusion press die openings, to dispose the liner bore openingat said end in uid-tight relation to the extrusion die openings,throughrwhch the material of a heated metal billet, disposed in saidliner, may be forced by movement of a ram projected within the said rstend opening of said liner.

2, The billet container substantially as set forth in claim 1,characterized by the wall of said mantle element being substantiallythicker than said liner element, and by said mantle and liner elementsbeing thermally shrunk-fitted tightly together by lirst causing thetemperature of the mantle element to exceed that of the liner elementduring assembly of said liner element within the bore of said mantleelement.

References Cited in the le of this patent UNITED STATES PATENTS1,943,802 Northrup Jan. 16, 1934 1,981,632 Northrup Nov. 20, 19341,987,458 Adams Ian. 8, 1935 2,182,819 Pisarev Dec. 12, 1939 2,229,680Somes Jan. 28, 1941 2,365,021 Strickland Dec. 12, 1944 2,452,197 KennedyOct. 26, 1948 2,461,765 Olt Feb. 15, 1949 2,669,647 Segsworth Feb. 16,1954 FOREIGN PATENTS 767,150 Germany Dec. 6, 1951

